Disc resonator integral inertial measurement unit

Abstract

Sensing motion of multiple degrees of freedom for an integral inertial measurement unit provided through the operation of a single centrally mounted planar disc resonator having a single driven mode in a single vacuum enclosure is disclosed. The resonator comprises a circumferentially slotted disc having multiple internal capacitive electrodes within the slots in order to excite a single in-plane driven vibration and sense in-plane vibration modes or motion of the resonator. In addition, vertical electrodes disposed below and/or above the resonator may also be used to sense out-of-plane vibration or motion. Acceleration sensing in three orthogonal axes can be obtained by sensing two lateral modes of the disc resonator in the plane of the disc from the internal electrodes and a vertical mode from the vertical electrodes.

1. A method of sensing, comprising the steps of:
 driving a disc resonator to excite a common driven mode of the disc resonator that induces three sensing modes of the disc resonator; and 
 demodulating three response signals from a plurality of sense electrodes to sense three response modes of the disc resonator; 
 wherein the three demodulated response signals comprise rotation measurement about three substantially orthogonal axes and the disc resonator comprises a circumferentially slotted disc and a plurality of drive electrodes and at least some of the plurality of sense electrodes are internal sense electrodes disposed within slots of the disc resonator and the common driven mode comprises a reactionless disc mode. 
 
     
     
       2. The method of  claim 1 , wherein the common driven mode and the three response modes operate at a common frequency. 
     
     
       3. The method of  claim 2 , wherein the disc resonator is tuned such that the common driven mode and the three sensing modes operate at the common frequency. 
     
     
       4. The method of  claim 1 , further comprising sensing acceleration along two substantially orthogonal lateral in plane axes of the disc resonator measured with the internal sense electrodes of the disc resonator. 
     
     
       5. The method of  claim 1 , wherein one of the three response modes comprises an in-plane elliptical mode for measuring an in plane rotation rate about a substantially perpendicular out of plane axis of the disc resonator. 
     
     
       6. The method of  claim 1 , wherein the plurality of sense electrodes comprise one or more vertical electrodes adjacent to a planar side of the disc resonator. 
     
     
       7. The method of  claim 6 , further comprising sensing acceleration along a substantially vertical out of plane axis of the disc resonator measured with the one or more vertical electrodes adjacent to the planar side of the disc resonator. 
     
     
       8. The method of  claim 6 , wherein two of the three response modes each comprise an out of plane rocking mode of the disc resonator for measuring an out of plane rotation rate about a substantially in plane axis of the disc resonator measured with the one or more vertical electrodes adjacent to the planar side of the disc resonator. 
     
     
       9. The method of  claim 8 , further comprising sensing acceleration along two substantially orthogonal lateral in plane axes of the disc resonator measured with the internal sense electrodes of the disc resonator; and
 sensing acceleration along a substantially vertical out of plane axis of the disc resonator measured with the one or more vertical electrodes adjacent to the planar side of the disc resonator sensing an out of plane mode of the disc resonator; 
 wherein a remaining one of the three response modes comprises an in-plane elliptical mode for measuring an in plane rotation rate about a substantially perpendicular out of plane axis of the disc resonator. 
 
     
     
       10. A sensor, comprising:
 a centrally mounted disc resonator including a drive electrode disposed internal to the disc resonator and a plurality of sense electrodes; 
 a drive circuit for applying a sinusoidal carrier voltage to the drive electrode to excite a common driven mode of the disc resonator that induces three sensing modes of the disc resonator; and 
 a sense circuit for demodulating three response signals from the plurality of sense electrodes to sense three response modes of the disc resonator, where the three demodulated response signals comprise rotation measurement about three substantially orthogonal axes; 
 wherein the disc resonator comprises a circumferentially slotted disc and a plurality of drive electrodes and at least some of the plurality of sense electrodes are internal sense electrodes disposed within slots of the disc resonator and the common driven mode comprises a reactionless disc mode. 
 
     
     
       11. The sensor of  claim 10 , wherein the common driven mode and the three response modes operate at a common frequency. 
     
     
       12. The sensor of  claim 11 , wherein the disc resonator is tuned such that the common driven mode and the three sensing modes operate at the common frequency. 
     
     
       13. The sensor of  claim 10 , wherein acceleration is sensed along two substantially orthogonal lateral in plane axes of the disc resonator measured with the internal sense electrodes of the disc resonator. 
     
     
       14. The sensor of  claim 10 , wherein one of the three response modes comprises an in-plane elliptical mode for measuring an in plane rotation rate about a substantially perpendicular out of plane axis of the disc resonator. 
     
     
       15. The sensor of  claim 10 , wherein the plurality of sense electrodes comprise one or more vertical electrodes adjacent to a planar side of the disc resonator. 
     
     
       16. The sensor of  claim 15 , wherein acceleration is sensed along a substantially vertical out of plane axis of the disc resonator measured with the one or more vertical electrodes adjacent to the planar side of the disc resonator. 
     
     
       17. The sensor of  claim 15 , wherein two of the three response modes each comprise an out of plane rocking mode of the disc resonator for measuring an out of plane rotation rate about a substantially in plane axis of the disc resonator measured with the one or more vertical electrodes adjacent to the planar side of the disc resonator. 
     
     
       18. The sensor of  claim 17 , wherein acceleration is sensed along two substantially orthogonal lateral in plane axes of the disc resonator measured with the internal sense electrodes of the disc resonator and along a substantially vertical out of plane axis of the disc resonator measured with the one or more vertical electrodes adjacent to the planar side of the disc resonator sensing an out of plane mode of the disc resonator; and
 wherein a remaining one of the three response modes comprises an in-plane elliptical mode for measuring an in plane rotation rate about a substantially perpendicular out of plane axis of the disc resonator.